xii CONTENTS 



PAGES 



CHAPTER X 



The- Carbo?ij NUrogenj Sulfur and Phosfhorus Cycles 



Iixiportance of Bacteria In Cycles 97 



The Carbon Cycle 98 



The Nitrogen Cycle 99 



The Sulfur Cycle 102 



The Phosphorus Cycle 102 



CHAPTER XI 



Organic Matter and Its Transformation by Bacteria 



Quantity of Organic Matter 107 



Kinds of Organic Matter 108 



Origin 108 



Composition 109 



Function 109 



Decay IIO 



Ammonification 113 



Organisms Causing Ammonification 113 



Material Ammonified 114 



Moisture 115 



Aeration 115 



Reaction 115 



Food Requirements 115 



Importance of Process 117 



CHAPTER XII 



Nitrification 



Earliest Developments : 118 



Early Ideas 119 



The True Cause of Nitrification 120 



Distribution 122 



Factors Governing Nitrification 123 



Manure 123 



Oxygen 124 



Temperature 125 



Moisture 125 



Food 126 



Crop and Fallow 127 



Loss of Nitrates 129 



